The purpose of this study is to determine the effects of four procedures on blood flow and the oxygen delivery to oxygen utilization ratio in the ischemic forelimb. These procedures will be studied in the resting state as well as during local forelimb exercise (electrical stimulation of the motor nerves). The procedures to be studied are: 1) acute or long-term blood volume expansion; 2) administration of vasodilator agents such as tolazoline or papaverine locally (intra- arterially); 3) whole body exercise; and 4) combinations of 1, 2, and 3. Forelimb blood flow from both the muscle and skin vascular beds will be measured with graduated cylinders and stopwatch. The ratio of oxygen delivery to oxygen utilization in the forelimb beds will be computed from blood flow and oxygen content of arterial and venous blood. Ischemia will be produced by acute or periodic (over 4 weeks) intravenous dextran in Ringer's solution infusion. Whole body exercise will be accomplished by exercising the animal daily on a treadmill for 4 weeks. Moreover, since volume expansion is a systemic procedure and may have adverse cardiac effects, the cardiac changes produced by acute and long term volume expansion will be studied. Finally, the technique will allow the study of another question; that of the reactivity of new arterial channels (i.e., those which develop with time after occlusion) to various vasoactive stimuli.